Earth’s longest lifelines and fossil evidence of the earliest complex communities with descendants still slowly forming similar ‘modern’ forms of the stromatolites. Dr Brendan Burns, from the University of NSW School of Biotechnology and Biomolecular Sciences, takes a closer look at ancient life on Earth, one that produced amazing structures called stromatolites. Stromatolites are basically living rocks. If you tap on them it is like tapping on concrete but they are alive, formed very slowly over vast periods of time by perhaps the simplest and most ancient forms of life on Earth – bacteria. While microbial mats and stromatolites were not necessarily the first forms of life, it was the grouping together of different microorganisms that gave rise to the structures of microbial mats and stromatolites. Complex communities of microorganisms then evolved and adapted to work well together in a low oxygen environment. This assisted the survival of the entire ecosystem, making them one of the most prevalent ecosystems on early Earth.